Scenario: Geographic mirroring

This scenario describes an IBM® i high-availability solution that uses geographic mirroring in a two node cluster. This solution provides both disaster recovery and high availability.


Geographic mirroring is a PowerHA® technology where data is mirrored to a copy of the independent disk pool at the remote location. This solution provides disaster recovery in the event of a site-wide outage on the production system (System 1). In that situation, failover to the backup site (System 2) occurs, where operations can continue on the mirrored copy of the data. This solution provides a simple and less expensive alternative to external storage-based solutions, such as IBM System Storage® Global Mirror and Metro Mirror. However, geographic mirroring does not offer all the performance options that the external storage solutions provide.


This solution has the following advantages:
  • Provides availability for your business resources during planned outages
  • Provides availability for business resources during unplanned outages
  • Provides availability for business resources during a disaster
  • Enables data to remains current and may not need to be synchronized
This solution has the following restrictions:
  • There is no concurrent access to the disk pool. Only the production copy is normally accessed. However, you can detach the mirror copy for offline processing of a second copy of the data.
  • Potentially affects performance because increased central processing unit (CPU) is required to support geographic mirroring
  • Consider using redundant communication paths and adequate bandwidth


The following graphic illustrates this solution:

Cross-site mirroring with geographic mirroring

Configuration steps

Complete the following steps to configure the high availability technologies that are associated with this scenario using commands:

  1. Complete planning checklist for clusters
  2. Create a cluster
  3. Add nodes
  4. Start nodes
  5. Add nodes to device domain
  6. Create a cluster administrative domain
  7. Start cluster administrative domain
  8. Create an independent disk pool using Configure Device ASP.
  9. Add monitor resource entries
  10. Create device CRG
  11. Start a device CRG
  12. Use Vary Configuration to make the disk pool available.
  13. Perform a switchover to test the configuration.